This invention relates in general to gauging fixtures and in particular to an apparatus for automatically spin checking driven disc assemblies adapted for use in friction clutches.
Clutches are well known devices which are frequently employed in vehicles to selectively connect a source of rotational power, such as the crankshaft of an engine, to a driven mechanism, such as a transmission. Typically, a cover of the clutch is connected to a flywheel carried on the end of the engine crankshaft for rotation therewith. Between the flywheel and the clutch cover, a pressure plate is disposed. The pressure plate is connected for rotation with the flywheel and the cover, but is permitted to move axially relative thereto. A shift lever assembly is provided for selectively moving the pressure plate back and forth in the axial direction. The shift lever assembly is usually operated by a driver of the vehicle by means of a foot actuated pedal.
A driven disc assembly is disposed within the clutch between the pressure plate and the flywheel. The driven disc assembly is carried on an output shaft of the clutch, which forms the input to the transmission. The driven disc assembly includes a hub, which is splined onto the output shaft, and a support plate which is mounted on the hub for limited rotational movement. A plurality of friction elements are usually secured to the outer ends of the support plate. Springs or similar torsion dampening devices may be provided between the support plate and the hub. When the pressure plate is moved toward the flywheel, the friction elements of the support plate are frictionally engaged therebetween so as to cause the output shaft of the clutch to rotate with the flywheel, the cover, and the pressure plate. When the pressure plate is moved away from the flywheel, the driven disc assembly is released from such frictional engagement so as to disconnect this driving connection.
The length of travel of the pressure plate between the engaged and disengaged positions is typically rather small, typically from 0.050 inch to 0.100 of an inch. Accordingly, the driven disc assembly (which is selectively engaged and disengaged by the pressure plate) must be manufactured to have a thickness which is within closely maintained tolerances. Furthermore, the driven disc assembly must not be excessively warped or otherwise non-planar in shape. Otherwise, the pressure plate may undesirably contact the driven disc assembly when moved to the disengaged position.
In the past, a test fixture has been provided for measuring the amount of warpage of a driven disc assembly, referred to as spin checking the assembly. This prior test fixture included a splined hub, upon which the driven disc assembly to be tested was mounted, disposed between a stationary ring and a movable ring. After the driven disc was installed, a pneumatic cylinder was actuated to move the movable ring toward the stationary ring such that the driven disc assembly was frictionally engaged therebetween. This movement initially positioned the two rings apart from one another by a distance which was equal to the thickness of the driven disc assembly. Then, the movable ring was retracted a predetermined distance from this initial position using a mechanical shim. This predetermined additional distance represented the maximum amount of warpage which could be tolerated for the particular driven disc assembly. Next, a predetermined amount of torque was applied to the hub to rotate the driven disc assembly relative to the rings. This torque was generated by means of a weight supported at the end of a pendulum connected to the hub. If the driven disc assembly was able to rotate under the urging of this applied torque, then the amount of warpage was within acceptable tolerances. However, if the driven disc assembly was not able to rotate under the urging of this applied torque, then the warpage of the driven disc assembly was beyond acceptable tolerances.
Although this prior test fixture has been found to function satisfactorily, it will be appreciated that it was somewhat slow and, therefore, inefficient in the production environment. Furthermore, it required several manual operations to be performed by an operator. Lastly, other than the inability of the driven disc assembly to rotate under the urging of the applied torque, the fixture generated no external indication of whether the tested assembly was good or bad. Thus, it would be desirable to provide an improved spin checking apparatus which automatically determines whether the driven disc assembly is good or bad and which generates an external indication to the operator of the test results.